Tubulointerstitial disease (TI) is characterize by mononuclear infiltration, renal tubular atrophy and fibrosis. Two key determinants of TI progression are inflammation and tubular loss secondary to apoptosis. We have identified osteopontin as a gene up-regulated in TI in response to many types of renal injury. Osteopontin is expressed predominantly in renal cortical tubular cells, and in vitro studies have suggested that TGFb and EGF may be particularly important in disease related up- regulation of osteopontin. In vivo and in vitro functional studies have determined that osteopontin has both pro-inflammatory and renal protective properties. We propose that these effects are due to the ability of osteopontin to induce activation of the NFkappaB pathway and renal cell survival. In this proposal we will 1) identify cis- and trans-acting factors required for EGFv and EGF induced transcription of the osteopontin gene in vitro using transient transfection, gel shift and DNA footprinting assays, 2) determine the role of osteopontin in promoting renal cell survival by testing the effect of purified osteopontin and peptides on apoptosis of renal tubular epithelial cell fibroblasts and macrophages in vitro, the osteopontin receptors mediating protective effects, and the role of NFkappaB in osteopontin-induced renal cell survival, and 3) to delineate the mechanism of osteopontin mediated NFkappaB activation and survival by identifying the upstream signalling pathways and downstream effectors of apoptosis involved. These studies will greatly aid our understanding of TI and may lead to improved therapies.